1. Field of the Invention
The present invention relates to a liquid ejection head that ejects liquid such as ink for recording purposes.
2. Description of the Related Art
Liquid ejection heads having a structure adapted to be directly mounted by ink tanks, which are in other words liquid storing containers, for storing liquid (a so-called on-carriage structure) are known. Liquid ejection heads of the above-identified type include a liquid ejection substrate having a plurality of ejection ports and a housing in which a plurality of ink tanks can removably be loaded. The liquid ejection substrate is rigidly secured to the outer surface of the housing and the plurality of ink tanks are loaded in array in the inside of the housing. Each of the ink tanks contains an ink absorbent that is impregnated with ink and the ink absorbent is partly exposed to the ink outlet port of the ink tank.
Japanese Patent Application Laid-Open No. 2007-125770 discloses a liquid ejection head of the above-described on-carriage type. In the liquid ejection head disclosed in Japanese Patent Application Laid-Open No. 2007-125770, ink supply ports for supplying ink to the liquid ejection substrate are formed in the housing and a filter is arranged at each of the ink supply ports. Additionally, an electrical wiring substrate for electrically connecting the liquid ejection substrate and the liquid ejection apparatus main body is arranged on the outer surface of the housing.
The liquid ejection head disclosed in Japanese Patent Application Laid-Open No. 2007-125770 is provided with a system for supplying ink from the ink tanks to the liquid ejection substrate by pressurizing the ink absorbent at the ink outlet port of each of the ink tanks and forcing the absorbent into contact with the filter at the corresponding ink supply port of the housing at the time when the ink tanks are loaded in the housing. Therefore, when there is not any ink tank loaded in the housing typically because all the ink tanks are removed from the housing in an operation of replacing the existing ink tanks, the filters are exposed to the outside. As the filters are exposed to the atmosphere, the water content of ink becomes liable to evaporate so that, if the filters are exposed to the atmosphere for a long period of time, ink can be caught in the meshes of the inner tissues of the filters and also at the surface layers of the filters and become hardened to consequently clog the filters.
In view of the above-identified problem, the applicant of the present patent application looked into the feasibility of additionally providing the housing of a liquid ejection head with a tank connection unit that covers the ink supply ports where filters are arranged from the atmosphere and is adapted to be connected to ink tanks. However, as a tank connection unit is added to the housing, the filters are prevented from being clogged but the liquid ejection head can be upsized and become bulky.
The applicant of the present patent application also looked in the feasibility of further additionally providing the housing of a liquid ejection head to which a tank connection unit has already been added as described above with connectors and an electrical wiring substrate for electrically connecting the ink tanks with the liquid ejection apparatus main body.
An arrangement as described below can be conceivable to realize the above-described provisions. A plurality of connectors to be electrically connected to respective ink tanks are arranged on the inner surface of a part of the lateral wall of the housing and an electrical wiring substrate to be electrically connected to the liquid ejection apparatus main body is arranged on the outer surface of that part of the lateral wall. Then, the electrical wiring substrate and the terminals of the connectors are electrically connected. Thereafter, the liquid ejection apparatus main body and the ink tanks are electrically connected to each other as the electrode pads formed on the electrical wiring substrate are pressed against the respective electrode terminals as electrical contacts formed at the side of the liquid ejection apparatus main body.
Then, however, a plurality of apertures needs to be formed in the lateral wall of the housing so as to allow the connectors to run through the lateral wall and come out to the outside of the housing. As such apertures are formed, the stiffness of the wall, to which the connectors and the electrical wiring substrate are rigidly secured, will be reduced so that the reliability of the electrical contacts between the electrode pads of the electrical wiring substrate and the electrode terminals at the side of the liquid ejection apparatus main body can be put at risk. Moreover, if apertures are not formed in the wall of the housing where the electrical wiring substrate are to be rigidly secured but the wall is liable to be deformed at the time of establishing electrical contacts between the electrical wiring substrate and the liquid ejection apparatus main body, the reliability of the electrical contacts can also be put at risk.
The wall of the housing where the electrical wiring substrate is to be rigidly secured may be provided with one or more than one rib in order to improve the stiffness of the wall. Then, however, the ink tank sitting positions need to be selected appropriately in order to avoid any interference between the ink tanks and the rib or ribs. When the ink tanks are fitted to the wall at respective positions where the ink tanks are free from the rib or ribs, the plurality of ink tanks may not be tightly placed side by side. Then, the housing may have to be upsized. Thus, when one or more than one ribs are formed on the wall of the housing to which the electrical wiring substrate is rigidly secured and a tank connection unit is additionally fitted, the liquid ejection head will inevitably become further upsized and bulky.